1. Field of the Invention
The invention pertains to a liquid flow control device, especially a metering device, with an inlet for a liquid to be dispensed, especially as a metered quantity, the device comprising a valve seat, a sealing element cooperating with the valve seat, and an outlet for the liquid. The invention also pertains to a method, especially a metering method, for dispensing the liquid.
2. Description of the Related Art
The above-mentioned types of metering devices and metering methods are used, for example, for the rapid filling of containers, especially packages made of laminated material (cardboard with a PE coating), with a liquid (milk and juices). When these containers are being filled with a liquid, care must be taken to minimize the amount of foam produced. This is important, because, after they have been filled, the packages of laminated material are folded over at the top and then sealed by welding. If foam has formed, the inside surfaces of the upper edge of the package, which will later form the welded seam, will be wet. Leaks can therefore result when the edges of the package are welded, because the wetted areas prevent the PE coating from bonding properly.
If a container is being filled with a liquid containing vitamin C, the amount of air present in the headspace of the filled package must be small as possible. The air would react with the vitamin C, thus making it impossible to store the liquid in the sealed package for long periods without degradation. If foam were to form, however, it would be extremely difficult to obtain a headspace free of air.
For the reasons given above, there is therefore the need to avoid the formation of foam as completely as possible when containers are being filled with certain liquids.
If the liquid is added directly to a container by gravity, the impact of the liquid on the bottom of the container unavoidably creates foam. Before the stream of liquid even hits the bottom, vortices and constrictions develop in it, which prevent the stream from flowing calmly.
To reduce the formation of foam, tubular outlets have been developed, which create an almost completely laminar flow in the filling jet. These outflow pieces comprise several thin tubes, through which the liquid is conducted into the package. Above the outflow piece, a valve body is arranged, which can interrupt or release the infeed of the liquid from the supply tank and thus stop or restart the filling jet. It has been found, however, that, as a result of the friction of the liquid against the inside walls of the tubes, the individual jets are still too agitated.
An elaboration consists in arranging a cylindrical body with fine bores, the axes of which are parallel to each other, at the outlet of a metering device of the general type in question. In the constricted space of the bores, hardly any vortices form, which means that the liquid can flow with almost no agitation at all. A metering device with this type of cylindrical body is described in, for example, EP 0 754 144 B1. Nevertheless, when liquids are metered into packages, the known measures are often still incapable of suppressing foam formation sufficiently.
To prevent the formation of foam in a liquid being used to fill containers, EP 1588948 A1 discloses a liquid filling nozzle with an inlet for a liquid. The nozzle comprises a valve seat, a conical sealing element cooperating with the valve seat, and an outlet for the liquid. The sealing element can be brought into a first and a second open position, wherein the cross-sectional flow area between the valve seat and the sealing element and the angle at which the liquid is dispensed into the container to be filled in the one open position are different from those in the other open position.
GB 2308174 A discloses a liquid dispensing valve for filling containers with precise quantities of liquid. In a cylindrical housing with an inlet for the liquid, a flood piston, a dribble piston, and a drip piston are arranged concentrically from the outside to the inside; the pistons seal off the outlet of the liquid dispensing valve. The inner drip piston is connected by a piston rod to a compressed-air cylinder, which serves as a drive. A first spring is installed between the dribble piston and the drip piston and arranged concentrically to them. A second spring is installed between the dribble piston and the flood piston surrounding it. Finally, the flood piston is supported by way of a third spring against the housing of the liquid dispensing valve. In the Area of the outlet opening, the pistons have walls sections with similar angles of inclination. By means of the piston rod, the pistons, which are connected to each other by springs, can be opened and closed as a function of the stroke of the piston rod. To fill a container with liquid, first the outer flood piston and the two pistons arranged inside it, namely, the dribble piston and the drip piston, are all opened completely, so that most of the liquid (approximately 95%) enters the container through the ring-shaped gap between the outer flood piston and the outlet, which serves as the valve seat. To add the remainder of the liquid to the container, the liquid dispensing valve is closed, and then the piston rod is raised to such an extent that either only the central drip piston or both the drip piston and the dribble piston surrounding it are raised, so that the remaining quantity of the liquid drips or dribbles into the container.
DE 22 09 772 A discloses a liquid flow control device with an inlet for a liquid such paint. The liquid flow control device comprises a sealing piece arranged movably in a filling head; the sealing piece has a valve plunger, which can be brought to rest against a conical circumferential surface on the outflow nozzle of the filling head. Inside the sealing piece there is a valve rod, which can be brought to rest against the valve seat of a central outflow opening at the bottom of the sealing piece. The valve rod can be moved back and forth in the sealing piece by means of a piston plate, which is spring-loaded from above and which can be actuated from below for certain periods of time by pressing means. The sealing piece first opens the outlet of the outflow nozzle to the maximum degree. After most of the desired quantity of liquid has run into the vessel to be filled, the valve plunger is lowered to such an extent that the circumferential surface of the sealing piece is located a short distance away from the valve seat of the outlet, so that the liquid to be added to the container can pass through only a ring-shaped gap between the sealing piece and the valve seat. Then the sealing piece is pressed firmly onto the valve seat. At the same time, however, compressed air is used to continue to hold the valve rod in its open position against the action of the spring. Now only a small amount of the liquid to be added can flow through the central outflow opening into the vessel to be filled. As soon as the correct weight has been obtained in the vessel, the valve rod is moved immediately downward by the compression spring toward the valve seat, as a result of which the liquid feed is completely stopped.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.